DecoratedWindow on Tao

DecoratedWindow is the same Composable across every backend. On Tao it opens a native OS window, mounts a Skiko surface and gives you a TitleBar slot you can fill with arbitrary Compose content — including draggable regions and per-OS button layouts.

TL;DR

• One Composable, three OSes — title bar inset, traffic lights and snap zones handled per platform.
• useNativeTitleBar = false (default) gives you the custom Compose title bar slot.
• useNativeTitleBar = true keeps the OS-drawn frame and chrome.
• Drag regions are declared with the standard Modifier.windowDragHandler / hit-test exclusions.
• Resize, minimise, maximise and full-screen are wired into WindowState.

Install

plugins {
    id("dev.nucleusframework")
}

dependencies {
    implementation("dev.nucleusframework:nucleus.nucleus-application:<version>")
    implementation("dev.nucleusframework:nucleus.decorated-window-tao:<version>")
}

Quickstart

import androidx.compose.foundation.layout.*
import androidx.compose.material3.Text
import androidx.compose.runtime.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.*
import androidx.compose.ui.window.rememberWindowState
import dev.nucleusframework.application.*
import dev.nucleusframework.window.core.*

fun main() = nucleusApplication(backend = NucleusBackend.Tao) {
    val titleBarStyle = TitleBarStyle(
        colors = TitleBarColors(
            background = Color(0xFF1A1D24),
            inactiveBackground = Color(0xFF15181D),
            content = Color(0xFFE6E6E6),
            border = Color.Transparent,
        ),
        metrics = TitleBarMetrics(height = 36.dp),
    )

    NucleusDecoratedWindowTheme(isDark = true, titleBarStyle = titleBarStyle) {
        DecoratedWindow(
            onCloseRequest = ::exitApplication,
            state = rememberWindowState(size = DpSize(1024.dp, 720.dp)),
            title = "Tao Demo",
            minimumSize = DpSize(640.dp, 480.dp),
        ) {
            TitleBar(modifier = Modifier.macOSLargeCornerRadius()) { state ->
                Text("Tao Demo", Modifier.align(Alignment.CenterHorizontally))
            }
            Box(Modifier.fillMaxSize()) { /* app content */ }
        }
    }
}

How it works

nucleusApplication { } resolves the backend and exposes DecoratedWindow on NucleusApplicationScope. On Tao, that overload delegates to dev.nucleusframework.window.tao.ApplicationScope.DecoratedWindow, which opens a TaoWindow and mounts a ComposeScene against the native surface.

Inside the content lambda you get a NucleusDecoratedWindowScope. From there:

• nucleusWindow returns the backend-agnostic NucleusWindow handle (focus state, minimise / maximise / fullscreen flows, icon, minimum size).
• nucleusWindow.unsafe.taoWindow is the raw TaoWindow if you need it.
• TitleBar { state -> … } declares the title bar slot. Pass a Modifier.macOSLargeCornerRadius() to opt into the rounded-corner look on macOS 11+.

Title bar styling is shared with the AWT backends — TitleBarStyle, TitleBarColors, TitleBarMetrics and NucleusDecoratedWindowTheme all live in decorated-window-core. So the same theme works whether you swap the dependency to -tao, -jbr or -jni.

Reference

DecoratedWindow parameters

Scope members

interface NucleusDecoratedWindowScope : DecoratedWindowScope {
    val nucleusWindow: NucleusWindow
}

interface NucleusWindow {
    val isFocused: Boolean
    val focusFlow: StateFlow<Boolean>
    fun setMaximized(value: Boolean)
    fun setFullscreen(value: Boolean)
    fun setMinimumSize(size: DpSize?)
    fun setIcon(painter: Painter?)
    fun close()
    val unsafe: NucleusWindowUnsafe   // .taoWindow, .taoHandle
}

Useful modifiers

• Modifier.macOSLargeCornerRadius() — opt into macOS 11+ rounded corners.
• Modifier.newFullscreenControls() — relayout title bar buttons for fullscreen.
• Modifier.windowDragHandler(window) — make a region act as a drag handle.

Notes

• macOS requires -XstartOnFirstThread — the Nucleus Gradle plugin handles it.
• Native title bar mode (useNativeTitleBar = true) skips the Compose slot and hands chrome back to the OS. Use it for tools where users expect 100% native frames.
• For multi-window apps, call DecoratedWindow multiple times from the same nucleusApplication block. Each window gets its own NucleusWindow. See DecoratedWindow overview.